A small molecule emitting in the near infrared region with pH sensitivity for visualization mitochondria under super-resolution microscopy.

Abstract Small molecules emitting in the NIR for tracking mitochondrial pH alteration with super-resolution are expected to play an essential role in biomedical applications. Herein, two small molecules based on pyridinium salt (P1 and P2) have been synthesized and systematically investigated. It was found that pyridinium salts P1 and P2 emitted in the NIR (about 610 nm), which could detect pH changes from 2.0 to 11.0 with good linearity and high sensitivity. Importantly, P2 could precisely target cellular mitochondria in a real-time manner under stimulated emission depletion (STED). These results implied a chemical strategy with a potential application in super-resolution imaging and mitochondrial pH determination. Graphic abstract fx1 Highlights • Synthesis and investigation of small molecules based on pyridinium salt (P1 and P2). • Detection of pH changes from 2.0 to 11.0 with a good linearity and high sensitivity. • Uniform distribution of P2 within the cytosolic region and excluded from the nucleus. • Localization of P2 into mitochondria and sensitivity to mitochondrial environment. • Monitoring mitochondrial pH variation in a real-time under stimulated emission depletion (STED). [ABSTRACT FROM AUTHOR]